Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual é a arma externa com um carrinho de cabeça de carneiro?
 ###Tabelas: CREATE TABLE knights'_weapons_items_and_vehicles (knights'_weapons_items_and_vehicles_id AUTO_INCREMENT PRIMARY KEY, Knight VARCHAR, Weapon/item VARCHAR, External weapon VARCHAR, Shield animal VARCHAR, Cart VARCHAR) CREATE TABLE list_of_nyagatare_sectors_by_population_2012 (list_of_nyagatare_sectors_by_population_2012_id AUTO_INCREMENT PRIMARY KEY, Rank in Nyagatare Sectors, 2012 INT, Sector VARCHAR, Area in sqkm INT, Population August 15, 2012 INT, Population, August 15, 2002 INT, Population Change 2002-2012 (%) VARCHAR, Population Density 2012 (km 2 ) INT) CREATE TABLE athletes_of_the_year (athletes_of_the_year_id AUTO_INCREMENT PRIMARY KEY, Year INT, Winner VARCHAR, Sport VARCHAR, Hometown VARCHAR, College VARCHAR) CREATE TABLE best_bowling_figures (best_bowling_figures_id AUTO_INCREMENT PRIMARY KEY, Player VARCHAR, Overs INT, Figures VARCHAR, Opponent VARCHAR, Ground VARCHAR) CREATE TABLE record_vs._other_opponents_at_least_15_games_played (record_vs._other_opponents_at_least_15_games_played_id AUTO_INCREMENT PRIMARY KEY, Missouri vs. VARCHAR, Overall Record VARCHAR, at Columbia VARCHAR, at Opponents Venue VARCHAR, at Neutral Site VARCHAR, Last 5 Meetings VARCHAR, Last 10 Meetings VARCHAR, Current Streak VARCHAR)  
SELECT External weapon FROM knights'_weapons_items_and_vehicles WHERE Cart = ramhead cart